A woman and two children have been found dead at a house, police said.
The 34-year-old woman and two girls, aged nine and four, were discovered at a property in Midcroft, Ruislip, at 6.40pm last night.
Scotland Yard said that detectives from the Homicide and Serious Crime Command were investigating.
At this stage, the deaths are being treated as unexplained and next of kin have been informed.
More top news
The London Marathon brings together thousands of people raising money for charity - not to mention some rather unusual costumes.
Planning on going to the London Marathon tomorrow? Read our handy guide first!
Celebrations to mark St George's Day have started in Trafalgar Square with feasts and tea to be found in abundance.